[cairo] Limitation of recording surface

[Adrian Johnson]

On 10/02/15 03:09, Bernhard R. Fischer wrote:
> I solved the problem.
> What I did was to cut out holes of a polygon in a group by using 
> CAIRO_OPERATOR_CLEAR and then painted the group to the PDF surface 
> (pop_group_to_source(), paint()).
> 
> Although this works fine with image surfaces it seems that this operation is 
> not supported (or not implemented correctly) in the PDF backend as well as in 
> the SVG backend.

CAIRO_OPERATOR_CLEAR is not supported by pdf so is implemented using
fallback images.